Xenon is a very efficient anaesthetic gas, however it is an expensive and a rare resource. Recycling can significantly reduce the high costs associated with its use as anaesthetic. Two different xenon-recycling approaches can be taken: internal recycling (performed inside the Anaesthesia Gas Machine—AGM) and external recycling (performed outside the Anaesthesia Gas Machine—AGM). Two solutions have been proposed for internal recycling (bibliography [1] and [2]): the first proposed by University of Porto (Faculty of Engineering—FEUP), considers the constant removal of carbon dioxide and nitrogen from a closed circuit AGM, using adsorption and/or membrane technology; the second, proposed by Nippon Oxygen Corporation, considers only the removal of nitrogen, consequently reducing the AGM purge waste.
Two different kind of technological solutions have been proposed for xenon external recycling:                High-pressures and/or cryogenic technologies—bibliography [3] to [7].        Adsorption based technologies—bibliography [8] and [9].        
The first kind requires the manipulation of pressure and/or temperature in order to condensate xenon from the anaesthetic gas mixture. This process is used thoroughly in xenon industrial separation from air, however, the high volume, noise and power consumption of the required equipment make this process less attractive for smaller scales.
The second kind requires the use of specific adsorbents in order to selectively adsorb some of the components of the anaesthetic gas mixture. After treatment, the recycled xenon is usually pressurized in a gas cylinder.